Effects of Synthetic Luteinizing Hormone-Releasing Hormone/Follicle Stimulating Hormone-Releasing Hormone (LH-RH/FSH-RH) on Serum LH, Serum FSH and Ovulation in Anestrous Ewes2

Abstract

Five anestrous ewes were each treated intramuscularly with a total dose of 400 µg synthetic LH-RH/FSH-RH, given in two equal doses at a 4-hr, interval. Five control ewes were identically treated with carrier medium, acidified saline. Laparotomies were conducted 2 days before and 3 days after the treatment and presence of corpora lutea was used as an indication of ovulation. Double antibody radioimmunoassays were used to quantitate both serum LH and FSH concentrations before and after treatment. The mean peak concentration of serum LH and FSH of the ten treatments in the five LH-RH/FSH-RH treated ewes was 39.1±6.8 and 246±27 ng/ml, respectively. The mean times of occurrence of the LH and FSH peaks after intramuscular treatment with synthetic LH-RH/FSH-RH were 96±15 and 101±11 min., respectively. There was considerable variation in magnitude of LH and FSH release as well as the shape of the curves after treatment with LH-RH/FSH-RH between ewes and within the same ewe after two identical treatments. Ovulation occurred in three of the LH-RH/FSH-RH treated ewes and one of the saline treated control ewes, indicating that these ewes were all close to spontaneous ovulation probably due to the onset of the breeding season. There seemed to be little correlation between magnitude of serum LH or FSH concentrations and ovulation in the ewes treated with synthetic LH-RH/FSH-RH. Copyright © 1972. American Society of Animal Science. Copyright 1972 by American Society of Animal Science